Process of producing armor-plates for warships and other steel articles without case-hardening.



UNITED STATES PATENT onnion.

ANGELO LUGERTINI, TERNI, ITALY.

rnocnss or rnonucmo ARMOR-ZPLATES non WARSHIEPS an; enema s'rnnne'nrronn's wrrnou'r casn-mnnnnme.

1,110,395. No Drawing.

Patented Sept. 15, 1914.

To all whom it may concern Be 1t known that I, ANGELO LUCERTINI, a

5 subject of the King of Italy, and residing at 2 Via Mazzini Terni, Italy, have invented certain new and useful Improvements in the Process of Producing Armor-Plates for Warships and other Steel Articles Without Case- Hardening, and of which the following is a.

specification.

This invention relates to processes for manufacturing armor lates and other steel articles of the type in which the plate or the like has imparted to it the necessary toughness and hardness without case hardening.

The object of the present invention is to provide an improved process of the above kind for manufacturing armor .plates and;

the like. I

The steel used n the present process contains iron, carbon, silicon, sulfur, phos' phorus, manganese chromium and nickel in such proportions that it is capable-of being hardened without cementation.

It has been found that the best results are obtained with a steel containing the abovementioned elements in the following proportions:- I

Carbon From 0.70 to 0.95 Silicon From 0.100 to 0.200% Sulfur Not more than 0.03 Phosphorus Not more than 0.03 Manganese From 0.20 to' 0.30 Chromium From 2.50 to 3.50 Nickel From 3.0 to 4.0 Iron From 90.99 to 95.50

The preferred composition of the steel is as fo1lows:C 0.88%, Si=0.15%, S=0.03 I:0.03%, Mn=0.26%, Cr="3.40%, N1: 3.80%, Fe=91.4.5%.

According to the character desired in the final product, and according to the requirements of the process the proportions of these constituents may be varied. For example, in order to render the metal less resistant to the development of toughness and to prevent the development of brittleness, it is well to keep the proportions of sulfur, phosphorus and manganese as low as possible, the favorable influence of manganese 'not being necessary in the presence of high percentages of carbon and chromium. The percentages of nickel and chromium may also be modified, but not too widely, because otherwise in addition to the other drawbacks, the thermic treatment may be rendered more diflicult.

The metal is cast in suitable molds of the usual type. It is preferable that the ingot when taken out of the mold should be althe proper temperature for rolling it is convenient to again lower the temperature to about 450 C. Although this treatment has a useful influence and is sometimes indispensable, the ingot may also be treated according to the process generally used in the art provided the ingots are of a good metallic composition and not very large or they may also be large if the rolling mill isa very powerful one. The ingot, as soon as it is removed from its mold, may therefore be transferred directl to the heating furnace of the rolling mill a er lowering the temperature.

For rolling, the ingot is introduced into the heating furnace of the rolling mill, care being taken to avoid too great a dliference of temperature between the ingot and the furnace and the heating is carried on uniformly throughout the progress of the operation. The rolling is started at a temperature of I about 1150 C. and carried out preferably in more than one heating, and in every case must be carried out in several passes. After the rolling is finished and the plate is placed in the furnace for the thermic treatments, the temperature of the said furnace is slowly, gradually and uniformly lowered to about 400 C. and then again raised to a temperature of about 590610 C. In carrying-out this treatment it is well to first adopt an annealing system which consists in annealing at two difl'erent temperatures, namely, a high temperature annealing at a temperature of about 750900 0., and a low temperature annealing at about 590. to 630 0., the annealing at low temperature being followed by a tempering at low temperature. After this thetransformation of the granular into a fibrous structure is nearly finished.

A piece of the arm or plate can then be broken I ined.- If the result is not satisfactory it will be suflicient to repeat the tempering at a temperature of from 80100 (3., and occasionally it may be necessary to again anneal ,5 the plate or to temper it at a high temperature. Before the plate is subjected to the next operation it is annealed at low temperature, (about 600 C.) followed by correcting in a press in order to remove irregularities which may have been caused by the various manipulations to which the plate has been submitted.

The above described process, though there is no case hardening, is rather long, but it is particularly suitable for the most unfavorable case of very thick armor plates in which the metallic composition is not too good.

The plate after the above described operations, is treated in suitable-machines in order to reduce it approximately to the dimensions and shape required, and is then planed and ground down to its proper thickness onthe surface which for example is to form the outer skin of the ship. I The planing and'grinding of the outer face ofthe plate in order to remove the. decarburized surface is an operation of importance in the process. If, however, the

percentage of carbon is Very high, and the heating for the rolling and forging operations or the thermic treatments, appears not to have too much decarburized the surface of the plate, the planingand grinding operations may also be omitted, and in this case a careful hammering and cleaning of the surface will be sufiicient. Thereupon the plate is bent in the press to its proper shape, after having been heated to a low temperature such as 600 C. or a little more, and if found necessary this heating may be repeated.

If for special reasons of conformation, heating to a high temperature cannot be avoided, care should'be taken that the temperature employed is not unnecessarily high, the plate being then again subjected to annealing or tempering at a low temperature. If it is deemed necessary owing to the numerous heat treatments to which the plate may have been subjectedafter the planing 5o operation, the outer face of the plate may be protected with carburi zingmaterial such as soot, graphite or the like. The plate is then ready to receive the final treatment for difl'erential tempering. This operation is more difficult and requires greater care with a plate according to the present invention than is the case with plates reduced by the usual processes. The most-important point is to render this operation much more rapid than usual, with the object of obtaining a small depth of tempered zone, the heating being at a temperature of about 860 on the outer smooth surface to be hardened, and

p a temperature of about 600 C. or even less,

on the inner face.

The operation is more difficult for plates of small thickness. This difficulty can be overcome, however, by the following means :(1) The use of a source of heat of a very high heating power. (2) The art-ificial increase of the thickness of the plate by interposing a metallic layer between it and the sand bed, and (3) Modifying the composition of the metal by lowering its percentage of nickel below the established 5 limit or even suppressing it altogether. The plate is then corrected in a press and submitted to finishing processes of known character. After the differential heating the plate is quenched. 30

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A process for producing armor plates and other steel articles comprising the fol- 5 lowing steps: cooling and reheating the ingot preparatory to rolling, rolling the ingot, heating and cooling the rolled plate so as to transform the metal from a granular to a fibrous structure, reducing the plate approximately to the required shape and size, heating one side of the plate to.- a high temperature for hardening, and heating the other side to a low temperature for toughening and quenching the" plate.

2. A process for producing armor plates and other steel articles comprising the following steps: .cooling the ingot gradually and-uniformly throughout its whole. mass, heating the ingot to a high temperature and gradually cooling it, heating the ingot to a temperature which is lower than the before mentioned temperature and is maintained for some hours after which the ingot is heated and then rolled, heating and cooling the rolled plate so as to transform the metal from a granular to a fibrous structure, reducing the plate approximately to the requlred shape and size, heating one side of theplate to a high temperature for harden- 0 ing and'heating the other side to a low temperature for toughening, and quenchingthe plate.

. 3.'A process for producing armor plates and other steel articles comprising the following stepszheating the ingot at a high temperature, heating the sameat a low temperature, rolling the ingot, annealing the rolled plate at a high temperature, annealing the same at a low temperature, reducing the plate approximately to the required shape and size, heating one side of the plate .to a high temperature for hardening and heating the other side to a low temperature for toughening.

4. A process for producing armor plates and other steel articles comprising the following steps: heating the ingot at a high temperature, heating the same at a low temperature, rolling the ingot, heating and 130 cooling the rolled plate so as to transform the metal from a granular to a fibrous structure, reducing the plate approximately to the required shape and size, planing and grinding the plate on one face, heating the face which has been planed and ground to a high temperature for hardening and heating the other side to a low temperature for toughening.

5. A process for producing armor plates and other steel articles comprising the following steps: taking an ingot of steel; heating to about 1150 0.; rolling the ingot in several passes; lowering the temperature of the rolled plate to 400 0.; raising the temperature of the plate to about 590-610 0.; annealing the plate at about 600 0.; heating one side of the plate for hardening and the other side for developing toughness and quenching the plate. 1

6. A process for producing armor plates and other steel articles comprising the fol lowing steps: taking an ingot of steel, heating the ingot to about 7 850 0., cooling the ingot to about 450 0. heating thejingot to about 620 0. for some hours, cooling the ingot to about 450 0.; gradually heating the ingot to about 1150 0. rolling the ingot in several passes; lowering the temperature of the rolled plate to 400 0.; raising the temperature of the plate to about 590-610 0.; annealing the plate at about 600 0.; heating one side of the plate for hardening and the other side for developing toughness and quenching the plate.

7. A process for producing armor plates and other steel articles comprising the following steps: taking an ingot of steel; heating to about 1150 0.; rolling the ingot in several passes; lowering the temperature of the rolled plate to 400 0.; raising the temperature of the plate to about 590 6l0 0.; annealing the plate at a temperature of about 750-900 0.; annealing the plate at a temperature of 590 to 630 0.; tempering the plate at a low temperature; annealing the plate at about 600 0.; heating one side of the plate for hardening and the other side filn; developing toughness and quenching the p ate.

8. A process for producing armor plates and other steel articles comprising the following steps: taking an ingot of steel, heating the ingot to about 750850 0., cooling the ingot to about 450 0., heating the ingot to about 620 0. for some hours, cool-- ing the ingot to about 450 0.; gradually heating the ingot to about 1150 0.; rolling the ingot in several passes; lowering the temperature of the rolled plate to 400 0.; raising the temperature of the plate to about 5906l0 0.; annealing the plate at a temperature of about 750 900 0.; annealing the plate at a temperature of 590 630 0.; tempering the plate at a low temperature; annealing the plate at about 600 0.; heating one side of the plate for hardening and the other side for developing toughness and quenching the plate. 4

9. A process for producing armor plates and other steel articles comprising the following steps: taking an ingot of steel; heat-.

ing to about 1150 0.; rolling the ingot in several passes; lowering the temperature of the rolled plate to 400 0.; raising the temperature of the plate to about 5906l0 0.; annealing the plate at a temperature of about 750-900 0.; annealing the plate at a tmperature of 590 to 630 0.; tempering the plate at a low temperature; again tempering at a low temperature; annealing the plate at about 600 0.; correcting the plate in the press; reducing the'plate to the desired form; heating the formed plate to at least 600 0.; heating one side of the plate to 860 0. while maintaining the other at 600 0. and quenching the formed plate.

In testimony whereof I have afiixed my signature in presence of two Witnesses.

ANGELO LUCERTINI. 

